Test-only helper colocated with production code now has a visible
.test-fixture.svelte boundary so eslint-boundaries and code search
do not confuse it for a production component. The internal alias was
also bumped from *Host to *Fixture for consistency. No behaviour
change. Felix #3 / Nora #3 on PR #629.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
